1. Field of the Invention
The present invention relates to a method of manufacturing a piezoelectric vibrator element, a piezoelectric vibrator element, and a piezoelectric vibrator.
2. Background Art
For example, in the electronic apparatus such as a cellular phone or a portable information terminal, there is used a piezoelectric vibrator using a quartz crystal or the like as a device used for a time source, a timing source for a control signal and so on, a reference signal source, and so on. As a piezoelectric vibrator of this kind, there has been known a device having a piezoelectric vibrator element hermetically encapsulated in a package provided with a cavity.
The piezoelectric vibrator element described above is provided with a base, and a pair of vibrating arm parts extending from the base in parallel to each other. In the piezoelectric vibrator element, the vibrating arm parts vibrate at a predetermined resonant frequency in directions of getting closer to and away from each other using base end parts (connection parts with the base) as the respective supporting points.
Here, as a method of adjusting the frequency of the piezoelectric vibrator element (the vibrating arm parts), there is a method of previously forming a weight metal film in a tip part of each of the vibrating arm parts, and adjusting the mass of the vibrating arm parts by partially removing (trimming) the weight metal films to thereby adjusting the frequency of the vibrating arm parts to a target value. For example, in JP-A-2013-118652 (Patent Document 1), there is disclosed a configuration in which the weight metal film is irradiated with a laser beam to partially eliminating the weight metal film to perform a coarse adjustment of the resonant frequency, and then the weight metal film is irradiated with an ion beam to perform a fine adjustment of the resonant frequency.
However, if the trimming is performed using a laser beam as in Patent Document 1 described above, there is a possibility that a burr is formed in a recessed part of the weight metal film formed by the trimming, or particles of the weight metal film scattered by the trimming adhere again to the surfaces of the vibrating arm parts. Further, if the burr or the particle is separated after the fine adjustment, there arises a problem that the frequency adjusted by the trimming varies.
Further, recently, due to miniaturization of electronic devices and so on, miniaturization of the piezoelectric vibrator and the piezoelectric vibrator element mounted on the electronic devices is requested. However, if the length of the vibrating arm part is shortened for miniaturizing the piezoelectric vibrator element, the variation in frequency increases. In contrast, if the thickness of the weight metal film is increased in order to reduce the variation in frequency, the trimming by the laser beam becomes difficult.